In the high-speed and high-density signal transmission among electronic devices and wiring boards, the signal transfer with a conventional electric wiring is now encountering limitation in enhancement of the speed and density due to the barriers including mutual interference and attenuation of the signals. For breaking down the barriers, a technique of connecting electronic devices and wiring boards with light, i.e., the so-called optical interconnection technique, is being developed. A polymer optical waveguide is receiving attention as an optical waveguide owing to the easiness in processing as a transmission path of light, the low cost, the high degree of freedom in wiring, and the capability of high-density wiring.
As the mode of the polymer optical waveguide, a rigid type produced on a rigid support base, such as a glass-epoxy resin, which is assumed to be applied to an optoelectronic board, and a flexible type having no rigid support base, which is assumed to interconnect boards, are considered as preferred examples.
The polymer optical waveguide is demanded to have high transparency (i.e., low optical transmission loss) and high heat resistance from the standpoint of the use environment and the component mounting of the equipment, to which the polymer optical waveguide is applied, and as a material for the optical waveguide, those using an epoxy resin, a (meth)acrylic polymer and the like are proposed (see Patent Documents 1 to 4).
However, there has been no evaluation of environmental reliability, for example; investigation on optical transmission loss and the like after a high temperature and high humidity shelf test and a temperature cycle test, and there has been no product that satisfies the demands.
For example, the epoxy resin disclosed in Patent Document 1 has good transparency at a wavelength of 850 nm and heat resistance around from 200 to 280° C., but there is no description relating to the evaluation of the environmental reliability, which is not investigated.
The (meth)acrylic polymer disclosed in Patent Document 2 is a material for an optical waveguide in a film form and has transparency with an optical transmission loss of 0.3 dB/cm at a wavelength of 850 nm, but there is no description relating to the evaluation of the environmental reliability, for example, specific test results of optical transmission loss and the like after a high temperature and high humidity shelf test and a temperature cycle test, which are not investigated. Similarly, there is no description relating to the evaluation of heat resistance, for example, specific test results of optical transmission loss and the like after a solder reflow test.
The (meth)acrylic polymer disclosed in Patent Documents 3 and 4 is a material for an optical waveguide in a film form and has transparency with an optical transmission loss of 0.5 dB/cm or less at a wavelength of 850 nm and a good optical transmission loss after the high temperature and high humidity shelf test, but there is no description relating to the evaluation of heat resistance, for example, specific test results of optical transmission loss and the like after a solder reflow test, which is not investigated.
The polyhydroxy polyether disclosed in Patent Document 5 has no ethylenically unsaturated group on a side chain, and the material for an optical waveguide in a film form using the polyhydroxy polyether is excellent in transparency and heat resistance, but there is no description relating to the evaluation of low flexibility, for example, a breaking elongation, which is not investigated.